JP3236475B2 - Manufacturing method of welded pipe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for welding a welded pipe, and more particularly to a method for manufacturing an ultra-thin welded pipe having a wall thickness ratio (t / D) of 1% or less by using a high frequency heating means. The present invention relates to a production method suitable for

[0002]

2. Description of the Related Art FIG. 10 is a view showing a general conventional example when a welded pipe is manufactured from a metal strip by a roll forming method using high-frequency heating means.

In FIG. 1, H denotes a metal band H, which is unwound by an uncoiler and a leveler (not shown), is flattened, and is continuously fed to a roll forming machine 1.

The roll forming machine 1 includes a guide roll 2 composed of a pair of left and right vertical rolls, breakdown rolls 3 composed of a pair of upper and lower horizontal rolls, and side cluster rolls 4 composed of a pair of left and right vertical rolls. ... and a pair of upper and lower horizontal rolls, a fin pass roll 5, 5, 5B
The metal band H is sequentially bent in the width direction, and is formed into an open pipe shape having a circular cross section in which both edges are opposed to each other. Thereafter, as shown in FIG. 11, the metal strip H formed into an open pipe shape is heated by the induction heating coil 10 of the high-frequency heating means until both edges 7, 7 are melted. Side edges are applied by squeeze rolls 6
7 is welded by welding while discharging molten metal as much as possible from between the end faces (hereinafter referred to as a high-frequency welding method).

[0005] When the composite heat source welding is performed using the high frequency heating means, the high frequency heating means 12 (see FIG. 10) is used.
After preheating both edges 7, 7 to a predetermined temperature by
TIG, MI provided above and near the squeeze roll 6
Both edges 7 and 7 are melted using an appropriate fusion welding means (not shown) such as G or laser, and a side pressure is applied by a squeeze roll 6 to perform abutment welding (hereinafter referred to as high frequency preheating combined melting). Welding method).

[0006] In any of the above welding methods, both edge portions 7 of the metal band H are formed during the forming process by the roll forming machine 1.
In the vicinity of 7, a tensile force greater than that of the other portions 8 acts, and the elongation and deformation occur in the longitudinal direction. That is, breakdown rolls 3, 3,... And side cluster rolls 4,
In 4,..., Tensile stress is generated in the vicinity of both edge portions 7, 7 to extend in the longitudinal direction, and compressive stress is generated in other portions 8, and contracted in the longitudinal direction. In the fin pass rolls 5, 5, 5B, a pair of upper and lower rolls acts so that the longitudinal extension of the metal band H becomes constant in the width direction. Occurs,
The elongation in the longitudinal direction is smaller than the average elongation and shrinks in the longitudinal direction, and a tensile stress is generated in the other portion 8,
The elongation in the longitudinal direction is greater than the average elongation, and the film is stretched in the longitudinal direction.

The buckling strength of the material is small, for example, a thin-walled tube having a wall thickness / outside diameter ratio (t / D) of more than 1% and 2% or less due to the repetition of stretching and contraction of both edges during the molding process. In the case of molding, both edges are buckled during the molding process, and a so-called edge wave is generated.

As a method for preventing the generation of the edge wave, a downhill molding method for adjusting the molding height or a plurality of rolls arranged at a short pitch in the longitudinal direction to increase the buckling strength of both edges are provided. There is a cage molding method that presses and restrains both edge portions. Further, there is a method of adjusting the difference in strain between both edges and other portions generated in the molding process by local heating or by cooling after local heating (JP-B-61-61914). Further, there is a method of combining the above methods to eliminate a difference in distortion between both edges of the metal strip and other portions to prevent generation of edge waves.

[0009]

When a welded pipe is manufactured by the above high frequency welding method or the simple fusion welding method using only appropriate fusion welding means such as TIG, MIG or laser, the t / D exceeds 1%. When the target is a thin-walled tube of 2% or less, it is possible to sufficiently prevent the generation of the edge wave by each of the conventional methods described above.

[0010] However, when an ultra-thin thin tube having a t / D of 1% or less is to be manufactured by the high-frequency welding method or the high-frequency preheating combined melting welding method, even if each of the conventional welding methods described above is used, Although no edge wave is generated on the exit side of the fin pass roll, there is a problem that an edge wave is generated immediately before the squeeze roll, and welding defects frequently occur. This is for the following reason.

FIG. 12 shows how the high-frequency current flows when a high-frequency current is applied to the metal band H in order to melt or preheat both edges 7, 7 of the metal band H, taking an induction method as an example. 5A is a plan view, and FIG. 5B is a side view.

FIG. 13 is a schematic diagram showing a deformation mode of the metal band H corresponding to the flow of the high-frequency current.
FIG. 1A is a plan view, and FIG. 1B is a side view.

As is apparent from FIG. 12, a high-frequency current indicated by an arrow in the drawing caused by magnetism given by the induction heating coil 10 is a circle of a metal band H formed in an open pipe shape near the induction heating coil 10. It flows in the circumferential direction and concentrates on both edge portions 7. Corresponding to this current distribution, both edge portions 7, 7 are heated to a high temperature, but the other portion 8 is hardly heated, so that a remarkable temperature difference occurs between both edge portions 7, 7 and other portion 8, Thermal distortion of both edge portions 7 is increased.

For this reason, as shown in FIG. 13, the edge portions 7, 7 are arranged in a direction indicated by an arrow in FIG.
Greatly extend in the longitudinal direction. As a result, for example, FIG.
As shown in FIG. 14A, a mouth-opening deformation in which the distance between the edges 7 is large is caused, and a warping deformation in which the edges 7 are curved upward as shown in FIG.

In each of the above deformations, since the metal band H is restrained by the squeeze roll 6 and the final fin pass roll 5B (see FIG. 10) before and after the deformed portion, the metal band H cannot be deformed by a certain amount or more. Then, a portion where a compressive stress is applied to both edge portions 7, 7 is generated, and this portion is locally buckled and deformed to generate an edge wave. The above phenomenon is the same when the resistance type high-frequency heating means is used.

Therefore, even when an ultra-thin walled tube having a t / D of 1% or less is produced by the high-frequency welding method or the high-frequency preheating / fusion welding method, a method of producing a welded pipe that does not generate edge waves is provided. Development was desired.

SUMMARY OF THE INVENTION An object of the present invention is to provide a high-frequency heating means capable of producing an ultra-thin tube having a t / D of 1% or less without generating edge waves even in the case of an ultra-thin tube. It is an object of the present invention to provide a method for manufacturing a welded pipe by using a high-frequency welding method or a high-frequency preheating combined melting welding method.

[0018]

Means for Solving the Problems The inventors have conducted various studies on the generation phenomenon of the edge wave and the means for preventing the same, and have found the following (1) to (3).

(1) The edge wave generated when an ultra-thin tube having a t / D of 1% or less is produced by a high-frequency welding method using a high-frequency heating means or a high-frequency preheating combined welding method is a metal which has been conventionally studied. High-frequency current flowing through the metal band for high-frequency melting heating or high-frequency preheating mainly heats only both edges, not due to the difference in strain caused by the difference in the molding amount between both edges of the band and other parts As a result, a difference in thermal strain occurs between both edges and the other portions, whereby both edges are stretched in the longitudinal direction of the metal strip, and edge waves are generated. However, by controlling the shape of the metal strip formed into an open pipe shape on the entrance side of the squeeze roll so as to draw an upwardly convex arc, it is possible to prevent generation of edge waves at both edges.

(2) In this case, it is not necessary to set the pass line height of the squeeze roll higher than the pass line height of the final fin pass roll which is the reference pass line height.
On the downstream side of the squeeze roll, the pipe restraining means whose pass line height is set lower than the pass line height of the final fin pass roll is arranged at a predetermined position, while adjusting the pass line height and the inclination angle of the squeeze roll. What you need to do.

(3) In the metal strip formed into an open pipe shape before the butt welding with the squeeze roll, both edges are not subjected to any deformation restraint by the roll or the like.
Since it can be deformed relatively freely, when a compressive force acts on both edge portions, it is deformed by a small force, and edge waves are generated very easily. However, the metal band after the abutment welding is weld-bonded at both edges thereof and is constrained in the circumferential direction, so that both edges are hardly deformed. Even when receiving a force equivalent to the level at which the edge wave is generated, no edge wave is generated, and by providing the pipe restraining means on the downstream side of the squeeze roll, both edges of the metal band after the impact welding are provided. There should be no problem even when the compression force is applied.

The present invention has been made based on the above findings, and its gist lies in the following method for manufacturing a welded pipe.

The metal band is formed into an open pipe shape by passing it through a roll forming machine, and the opposite edges are melt-heated by high-frequency heating means and then welded by squeeze rolls or preheated by high-frequency heating means. Then, in a welding pipe welding method of performing butt welding with a squeeze roll after melt heating using a fusion welding means, at least a pipe restraining means for restraining the welded pipe after the butt welding on the downstream side from the squeeze roll. Two of them are provided, and the pass line height of the upstream pipe restraining means of the pipe restraining means is set to be lower than the pass line height of the final fin pass roll of the roll forming machine. And the path line height and the inclination angle are determined by the two pipe restraining means and the final fin pass roll. Method for producing a welded pipe, characterized by adjusting set along the orientation of the strip.

L (G + L) / (G + 3L) ≧ J where J: distance between the final fin pass roll and the squeeze roll (mm) L: distance between the final fin path roll and the upstream pipe restraining means (mm) G: Separation distance (mm) between the upstream pipe restraining means and the downstream pipe restraining means

[0025]

The edge buckling, that is, the edge wave generated due to the amount of thermal distortion generated when both edge portions are heated using the high-frequency heating means described above, as shown in FIG. The attitude of the metal strip H formed into an open pipe shape on the side can be prevented by controlling the attitude so as to draw an upwardly convex arc.

The basic principle will be described as follows.

As shown in FIG. 1, when the side view of the metal band H has a shape that draws an upwardly convex arc on the entrance side of the squeeze roll 6, the squeeze roll 6 and a final fin path (not shown) are formed. Both edge portions 7 between the area with the roll,
Since 7 has a shape that is longer than the bottom portion 9, a tensile stress acts on both edge portions 7, 7 in a direction indicated by a solid line arrow in the drawing. As a result, the compressive stress acting on both edges 7, 7 in the direction indicated by the dotted arrow in the drawing due to the thermal strain caused by local heating of both edges 7, 7 in the high-frequency heating means 10 is canceled by the tensile stress, Both edges 7, 7
The edge wave is not generated because the compressive stress does not act on.

Here, the simplest and simplest method for controlling the attitude of the metal band H on the entrance side of the squeeze roll 6 so as to draw an upwardly convex arc is the final fin pass of the roll forming machine 1. The pass line height of the roll 5B is set higher than the reference pass line height, or the pass line height of the squeeze roll 6 is set lower or higher than the reference pass line height. However, the former method involves deformation in which compressive stress acts on both edge portions 7 on the exit side of the fin pass roll 5 immediately before the final fin pass roll 5B, so that an edge wave is generated at this portion. It cannot be adopted. The latter method cannot be adopted for the following reasons.

In this type of tube mill, as shown in FIG. 2, a bead cutting device for removing an external bead formed by arranging a plurality of support rollers 13 'and a cutting tool 14 in opposition is usually provided with a squeeze roll. 6 is provided on the downstream side. This bead cutting device includes a plurality of support rollers 13 ′ and a cutting tool 1.
4 are arranged to face each other and have a function of restricting the rotation of the metal strip H in the longitudinal direction, so that it can be treated as a fixed support point.

In the final fin pass roll 5B, the cross-sectional shape of the metal band H in this portion is usually formed into a desired final tube shape, and almost the entire circumference thereof is formed by the hole shape of the final fin pass roll 5B. And has a function of restraining the rotation of the metal band H in the longitudinal direction, so that this can also be regarded as a fixed support point.

Therefore, the metal band H before and after the squeeze roll 6
Can be regarded as a horizontal elastic beam whose one end is fixed by the final fin pass roll 5B and the other end is fixed or simply supported by the first pipe restraining means 13 composed of a bead cutting device. The relationship between each support point and the load point when the point of application of the load W is the position of the squeeze roll 6 and the bending moment generated in the metal band is as follows.

FIG. 5 shows a metal band H before and after the squeeze roll 6.
Is a diagram showing the relationship between each supporting point and load point and the generated bending moment M when is regarded as a horizontal elastic beam, and FIG. FIG. 4B shows a bending moment generated when the application point of the load W is set to the position of the squeeze roll 6 and the height of the pass line is set to be higher than the reference pass line height. ) Shows the bending moment generated when the application point of the load W is set to the position of the squeeze roll 6 and the height of the pass line is set lower than the height of the reference pass line. FIG. And the relationship between the positive and negative of the generated bending moment are shown.

Incidentally, the first pipe restraining means 13 is provided in FIG.
As shown in (a), a bead cutting means may be provided with a pair of upper and lower hole type rolls.

As can be seen from FIG. 5B, when the pass line height of the squeeze roll 6 is set higher than the reference pass line height, the generated bending moment M becomes a positive value near the entry side of the squeeze roll 6. Thus, the metal band H has a shape in which an upwardly convex arc is drawn.

However, in the vicinity of the exit side of the final fin pass roll 5B, the generated bending moment M becomes a negative value, and the metal band H
Has a downwardly projecting arc, and compressive stress acts on both edges of this portion to generate edge waves.

Also, as can be seen from FIG. 5 (c), when the pass line height of the squeeze roll 6 is set lower than the reference pass line height, on the contrary, the final fin pass roll 5B is turned off. Although the generated bending moment M near the exit side has a positive value, the generated bending moment M near the entrance side of the squeeze roll 6 has a negative value, and the metal band H in this portion has a downwardly convex arc shape. Thus, compressive stress acts on both edge portions of this portion, and edge waves are generated.

From the above, it can be understood that generation of edge waves cannot be prevented even if the pass line height of the squeeze roll 6 is adjusted.

However, as shown in FIG. 3, the distance between the first pipe restraining means 13 and the squeeze roll 6 from the center of the final fin pass roll 5B is L, and the first pipe restraining means is The second pipe restraining means 11 is disposed at a position where the separation distance from the center of the pipe 13 is G, and the pass line height Hf of the final fin pass roll 5B and the first pipe restraining means 13 are provided.
And the pass line height Hg of the second pipe restraining means 11 is set so that the squeeze roll 6 does not serve as a load application point and a fixed fulcrum.
g is the reference pass line height, the final fin pass roll 5
When the load W is applied below the pass line height Hf of B, the relationship between each supporting point, the point at which the load W is applied, and the generated bending moment M is as shown in FIG.

As shown in FIG. 6 (b), the formula of a curved beam fixed at both ends (see, for example, No. 10 on page 176, the 5th revised edition of Mechanical Engineering Handbook, published on February 1, 1974, Sanseido Co., Ltd.). ), The final fin pass roll 5B
Distance from the final fin pass roll 5B to “L”
(G + L) / (G + 3L) "is a positive value.

Therefore, the final fin pass roll 5B
And the metal band H between the regions up to the above-mentioned “L (G + L) / (G + 3L)” position has a shape in which an upwardly convex arc is drawn and both edges 7, 7 are elongated. Compressive stress does not act on the edges 7,7. On the other hand, in a region from the position of “L (G + L) / (G + 3L)” to the second pipe restraining means 11, the generated bending moment M
Becomes a negative value, the metal band H has a shape that draws a downward convex arc, and compressive stress acts on both edge portions 7.

On the other hand, the load W is set by setting the pass line height Hg of the second pipe restraining means 11 above the pass line height Hf of the final fin pass roll 5B which is the reference pass line height. 6C, the bending moment M generated on the exit side of the final fin pass roll 5B becomes a negative value, and the metal band H takes a downwardly convex arc shape as shown in FIG. 6C. A compressive stress acts on both edge portions 7,7.

Accordingly, the bending moment M generated at the exit side of the final fin pass roll 5B becomes a positive value, and the metal band H draws an upwardly convex arc, so that compressive stress acts on both edge portions 7, 7. To avoid this, the second pipe restraining means 1
It can be seen that the pass line height Hg needs to be set lower than the reference pass line height Hf.

As described above, the edge 7 of the metal band H before the impact welding is relatively free to deform because it is not restrained at all, and easily deforms even when a small compressive stress is applied. Although edge waves are generated, both edge portions 7, 7 after the abutment welding are performed.
Are welded and jointly constrained in the circumferential direction of the tube and are not easily deformed. Even if a compressive stress equivalent to a level at which a edge wave is generated in the metal band H before the impact welding is applied, the edge wave is hardly generated.

Accordingly, the second pipe restraining means 11
Is set below the reference pass line Hf, and the distance J (see FIG. 4) from the final fin pass roll 5B is determined by the above-mentioned “L (G + L) / (G
+ 3L) ”= Q, when the squeeze roll 6 is arranged at a position that satisfies Q ≧ J so as not to be the load application point and the fixed fulcrum of the elastic beam, the squeeze roll 6 may be placed on the entry side of the squeeze roll 6 before the impact welding Since no edge wave is generated due to a compressive stress acting on both the edge portions 7, 7, normal welding can be performed. Further, even if a compressive stress acts on the edge portion 7 on the downstream side of the squeeze roll 6, the edge portion 7 is hardly deformed due to abutment welding. It will be very minor.

In the above description, the squeeze roll 6 is arranged so as not to be a load application point and a fixed fulcrum of the elastic beam for the following reasons. That is, the second pipe restraining means 1
When the attitude of the metal strip H is controlled so as to draw an upwardly convex arc by setting the height Hg of the first pass line below the height Hf of the reference pass line, the pass line height Hs of the squeeze roll 6 is controlled. If the inclination angle θ (see FIG. 4 described later) is not adjusted, the squeeze roll 6 restrains almost the entire circumference of the metal band H in the circumferential direction. Fixed fulcrum), and a bending moment is generated in this portion, and both edge portions 7, 7 of the metal band H between the final fin pass roll 5B and the squeeze roll 6 are formed.
Compressive stress acts on a part of.

FIG. 7 shows a case where the squeeze roll 6 is arranged at a position where the separation distance J from the final fin pass roll 5B is "L / 4" and the pass line height Hs is changed to load the elastic beam. It is a figure which shows the relationship between each supporting point and load point at the time of acting as an application | support point, and generated bending moment.

As shown in FIG. 7 (b), the pass run height Hs of the squeeze roll 6 is controlled to an upwardly convex shape at the position of the squeeze roll 6, and the open pipe axis PC (described later) of the metal body H is controlled. 4) and acts as an application point of the upward load W, a bending moment M ′ (shown only on the upstream side of the squeeze roll 6) shown by a dashed line in the drawing is generated. The bending moment M shown by a solid line in the figure, which is generated when the second pipe restraining means 11 is set downward, becomes the bending moment M "shown by a dotted line in the figure, and the bending moment M" on the exit side of the final finpass roll 5B. Becomes a negative value.

As shown in FIG. 7 (c), the pass run height Hs of the squeeze roll 6 is adjusted from the open pipe axis PC of the metal body H whose posture is controlled to an upwardly convex shape at the position of the squeeze roll 6. Is also set downward and acts as a point of application of the downward load W, a bending moment M '(shown only on the upstream side of the squeeze roll 6) shown by a dashed line in the figure is generated, and the second pipe restraining means The bending moment M shown by a solid line in the figure, which is generated when 11 is set downward, becomes the bending moment M "shown by a dotted line in the figure, and the bending moment M" on the entry side of the squeeze roll 6 becomes a negative value.

As a result, the metal band H on the entry side of the squeeze roll 6 draws a downwardly convex arc, and the edge portion 7 before the impact welding is formed.
Compressive stress acts on the steel sheet to generate edge waves, making normal welding impossible.

Further, as described above, the squeeze roll 6 restrains substantially the entire circumference of the metal pair H in the circumferential direction, and thus serves as a fixed end fulcrum of the bent beam. Therefore, if the inclination angle θ (see FIG. 4 described later) is different from the inclination angle along the upward convex shape of the metal band H determined by the second pipe restraining means 11 and the final fin path roll 5B, A new bending moment is generated with this as a fixed fulcrum.

FIG. 8 shows the separation distance J as in FIG.
When the squeeze roll 6 is arranged at the position of “L / 4” and the pass line height Hs is made coincident with the open pipe axis PC of the metal body H having the upward convex shape, the squeeze roll 6 FIG. 6 is a diagram showing the relationship between each supporting point and load point and the generated bending moment when the inclination angle θ of the elastic beam is changed to act as a fixed fulcrum of the elastic beam.

As shown in FIG. 8B, the pass line height Hg of the second pipe restraining means 11 is changed to the reference pass line height Hf.
If the inclination angle θ of the squeeze roll 6 is set smaller than the inclination angle of the metal body H whose attitude is controlled to have an upwardly convex shape by setting the inclination angle θ below, a negative bending moment is generated in the squeeze roll 6. The bending moment M shown by a solid line in the figure, which is generated when the pipe restraining means 11 is set downward, becomes a bending moment M '(shown only on the upstream side of the squeeze roll 6) shown by a dotted line in the figure, and The bending moment M ′ on the entry side of No. 6 becomes a negative value.

Further, as shown in FIG. 8C, when the inclination angle θ of the squeeze roll 6 is set to be larger than the inclination angle of the metal body H whose posture is controlled to the upward convex shape in the same manner as described above, Since a positive bending moment is generated in the squeeze roll 6, the bending moment M shown by a solid line in the figure and generated when the second pipe restraining means 11 is set downward is a bending moment M '(squeeze line) shown by a dotted line in the figure. Only the upstream side of the roll 6 is shown), which is preferable from the viewpoint of preventing generation of edge waves. However, in this case, squeeze roll 6
Abruptly deforms the metal body H near the entry side of the squeeze roll 6, the metal body H is rubbed by the lower flange 6a (see FIG. 4 described later) of the squeeze roll 6, and roll flaws are generated.

As a result, in both cases shown in FIGS. 7 and 8, the metal band H on the entry side of the squeeze roll 6 draws a downwardly convex arc, and compressive stress acts on the edge portion 7 before the abutment welding. However, edge welding occurs and normal welding cannot be performed, or roll flaws occur.

Accordingly, the squeeze roll 6 has a pass line height Hs and an inclination thereof along the upward convex shape of the metal band H determined by the second pipe restraining means 11 and the final fin pass roll 5B. It is necessary to adjust the angle θ so that it does not become an elastic beam, that is, a load supporting fulcrum and a fixed fulcrum of the metal body H.

FIG. 4 is a schematic diagram showing an adjustment mode for preventing the squeeze roll 6 from being any of the load application point and the fixed fulcrum of the elastic beam. According to the shape, the pass line height Hs of the squeeze roll 6 is set to a height different from the reference pass line Hf, in other words, the center of the open pipe axis of the metal strip H formed into an open pipe shape at the position of the squeeze roll 6. The inclination angle θ is set so as to coincide with the inclination of the metal band H while being made to coincide with the PC. Thereby, the squeeze roll 6 can be prevented from being any of the load application point and the fixed fulcrum of the elastic beam.

The positions where the edge wave is likely to be generated between the exit side of the final fin pass roll 5B and the entrance side of the squeeze roll 6 are the preheating temperature of both edges, welding conditions (welding speed, upset amount, etc.). In this case, the position of the squeeze roll 6 in the mill line direction is finely adjusted and the pass line height Hs
And the tilt angle θ should be finely adjusted at the same time.

The set position of the squeeze roll 6 in the mill line direction is determined by setting the second pipe restraining means 11 based on the final fin pass roll 5B and / or the first pipe restraining means 13 (a bead cutting device is also possible). After installing at the appropriate position,
There is no hindrance whether it is determined by an experiment or a curved beam calculation method. Further, when the present invention is applied to an existing pipe mill, the second pipe restraining means is based on the distance between the final fin pass roll 5B, the squeeze roll 6, and the first pipe restraining means 13 (a bead cutting device is also possible). Means 11
May be determined by the same method as described above.
However, since it takes a lot of time to determine the position by experiment, it is preferable that the final arrangement position is determined by bending beam calculation and then adjusted by experiment.

Further, since the second pipe restraining means 11 constituting the above simple support point can achieve its purpose only by pressing down the metal band H from above, only the upper roll having the hole shape is formed. May be provided.
In addition, the hole shape may be formed into a hole shape having the same or slightly larger curvature as the maximum outer diameter of the pipe to be shared, so as to be commonly used for various pipe outer diameters. Further, instead of the upper roll, a concave surface having a curvature R is formed in the longitudinal direction of the lower surface thereof along the curvature R (see FIG. 1) of the metal band H whose posture is controlled so as to draw an upwardly convex arc. A block body having an appropriate shape may be used.

[0060]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The method of the present invention will be described below in detail based on embodiments.

FIG. 9 is a schematic diagram showing the configuration of the entire apparatus for carrying out the present invention. In the drawing, 1 is a roll forming machine, 6 is a squeeze roll, 11 is a second pipe restraining means, 1
Reference numeral 3 denotes first tube restraining means, 12 denotes an induction-type high-frequency heating means including the induction heating coil 10, and H denotes a metal body.

The roll forming machine 1 is the same as the conventional apparatus, and includes a guide roll 2 and a plurality of breakdown rolls 3, 3,.
, Side cluster rolls 4, 4,..., Fin pass rolls 5, 5 and final fin pass roll 5B.
Are arranged in accordance with the pass line height Hf (see FIG. 3).

A second pipe restraining means is provided downstream of the final fin pass roll 5B constituting the roll forming machine 1 with a separation distance L as shown in FIG.
Further, a first pipe restraining means is provided downstream of the second pipe restraining means 13 with a separation distance G therebetween. Also,
The squeeze roll 6 is provided between the final fin pass roll 5B and the second pipe restraining means 13 at a position where the distance J from the final fin pass roll 5B is equal to or less than “L (G + L) / (G + 3L)”. ing.

The pass line height Hk of the first pipe restraining means 11 is made equal to the pass line height Hf of the final fin pass roll 5B which is the reference pass line height, while the second pipe restraining means 11 The pass line height Hg is set lower than the reference pass line height Hf.

Further, the squeeze roll 6 is provided in the same manner as in FIG.
As shown in the figure, along the metal body H formed in the shape of an open pipe whose attitude is controlled to draw an upwardly convex arc determined by setting the pass line height Hg of the second pipe restraining means 11 low. In this way, the pass line height Hs is made to coincide with the open pipe axis PC of the metal body H whose attitude is controlled, and the inclination angle θ is set.

The metal body H is continuously formed into an open pipe by the roll forming machine 1, the squeeze roll 6, the second pipe restraining means 13 and the first pipe restraining means 11 set as described above. The edges 7, 7 are heated to the melting temperature using the high-frequency heating means 12 and subjected to post-joint welding, or preheated to a predetermined temperature, and then TIG, M (not shown).
In the case of performing fusion welding by fusion welding means such as IG or laser, the attitude of the metal body H is controlled between the final fin pass roll 5B and the squeeze roll 6 so as to draw an upwardly convex arc. .

As a result, no compressive stress acts on the two edge portions 7, 7, and no edge wave is generated before the impact welding, so that the impact welding can be continuously performed without any problem. . Even if compressive stress acts on both edges 7 and 7 after the abutment welding on the exit side of the squeeze roll 6, the edge welding does not generate edge waves because the rigidity against deformation is increased by the abutment welding. Even if edge waves are generated, they will be extremely small.

Experimental Example 1 Outer diameter of 50.8 mm made of ferritic stainless steel (JIS-SUS420 equivalent)
For thin-walled tubes of various thicknesses (0.5 to 1.6 mm), the induction heating coil constituting the induction-type high-frequency heating means is placed at a position 120 mm upstream from the center of the squeeze roll to the center of the coil width. Are positioned so that the temperature at both edges at the center position of the squeeze roll is 1400.
° C, and an electric resistance welded pipe is manufactured by an electric resistance welding method in which a squeeze roll gives an upset amount of 0.4 mm and abuts at a pipe production speed of 40 m / min. The feasibility of using the method and the conventional method was investigated.

The squeeze roll is positioned at a distance J of 500 mm from the final fin pass roll, and the second pipe restraining means (only the upper roll) is positioned at a distance L of 1000 mm from the final fin pass roll. The first pipe restraining means (having upper and lower rolls) was arranged at a position where the distance G from the second pipe restraining means was 200 mm. Further, in the conventional method, the pass line heights of the rolls and the pipe restraining means are all equal (Hf =
Hs = Hg = Hk). In the method of the present invention, the height of the final fin pass roll and the pass line height of the first pipe restraining means are made to coincide (Hf = Hk), and the path of the second pipe restraining means is adjusted. The line height Hg is set to “Hg = Hf−20 mm”, and the pass line height Hs of the squeeze roll is set to “Hs = Hf−18 m”.
m ”and the inclination angle θ of the squeeze roll was set to an appropriate value of 3 °. The experimental results
The results are shown in Table 1.

[0070]

[Table 1]

As is apparent from Table 1, when the method of the present invention was used, no edge wave was generated at both edges before the impact welding at any thickness, and the impact was achieved without any problem. Could be welded.

On the other hand, in the conventional method, the wall thickness is not more than 0.
When the thickness is 8 mm (t / D = 1.57%) or more, edge waves are not generated at both edges before the impact welding due to the rigidity of the material itself, and the impact welding can be performed without any problem. Met. When the wall thickness was 0.6 mm (t / D = 1.18%), minute edge waves were generated at both edges before the butt welding, and the butt welding became unstable. By removing it, production was possible. However, the thickness is 0.6mm
(T / D = 0.98%), edge waves occurred frequently at both edges, and no impingement welding was possible. When both edges were not heated by the high-frequency heating means, no edge wave was generated at any thickness in both the conventional method and the method of the present invention.

Experimental Example 2 An outer diameter of 50.8 mm made of ferritic stainless steel (equivalent to JIS-SUS420),
For a thin-walled tube (t / D = 0.98%) with a wall thickness of 0.5 mm, the induction heating coil constituting the induction-type high-frequency heating means is placed at a position 120 mm upstream from the center of the squeeze roll to the center of the coil width. Is heated so that the temperature of both edges at the center position of the squeeze roll becomes 1400 ° C., and abuts at a pipe-forming speed of 40 m / min while giving an upset amount of 0.4 mm with the squeeze roll. When manufacturing an ERW pipe by the ERW welding method, the distance J from the final fin pass roll is 500 m.
m, and the first pipe restraining means is fixedly disposed at a position where the distance “L + G” from the final fin pass roll is 1900 mm, and the pass line height Hg is adjusted to an appropriate value “Hg = Hf”. −20 mm ”, the distance L of the second pipe restraining means from the final fin pass roll is variously changed, in other words, the final fin pass roll and the second
The distance L between the pipe restraining means and the distance G between the pipe restraining means are variously changed, and the pass line height Hs and the inclination angle θ of the squeeze roll are variously changed to investigate whether or not production is possible under each condition. did. Table 2 shows the experimental results.
Are shown together with each setting condition.

In the experiment, the position of the second pipe restraining means in the mill line direction was changed for the convenience of the apparatus. However, the second pipe restraining means may be fixedly arranged and the arrangement position of the squeeze roll may be changed. Is as described above.

[0075]

[Table 2]

As is clear from Table 2, the arrangement position of the squeeze roll with respect to the second pipe restraining means, the pass line height Hg of the second pipe restraining means, the pass line height Hs of the squeeze roll, and the inclination angle θ are shown in Table 2. In the present invention examples (Nos. 1 to 3) which were set to appropriate values, generation of edge waves was not recognized at both edges before the butt welding.

On the other hand, the pass line height Hs and the inclination angle θ of the squeeze roll are appropriate values, but the installation position is “J> Q = L (G + L) / (G + 3L)” and the comparative example is inappropriate. In (No. 4), edge waves were generated at both edges from near the entry side of the squeeze roll to downstream. In addition, the squeeze roll installation position and the inclination angle θ are appropriate, but the pass line height Hs is too high and an inappropriate comparative example (No.
In 5), edge waves were generated at both edges near the exit side of the final fin pass roll. Furthermore, the comparative example (No. 6) where the installation position of the squeeze roll and the inclination angle θ are appropriate but the pass line height Hs is too low is inappropriate, and the installation position and the pass line height Hs of the squeeze roll are A comparative example (N
In o. 7), edge waves were generated at both edges near the entry side of the squeeze roll. In addition, the squeeze roll installation position and the pass line height Hs are appropriate, but in the comparative example (No. 8) where the inclination angle θ is large and inappropriate, a roll flaw occurred.

In each of the above experiments, the electric resistance welding method was used, and the display of data was omitted. However, both edges of the metal body were preheated to a predetermined temperature by high-frequency heating means. Similar results can be obtained when applied to a so-called high-frequency preheating combined welding method, in which both edges preheated by fusion welding means such as TIG, MIG, and laser are heated to the melting temperature and heated by abutment welding. Needless to say.

[0079]

According to the method of the present invention, if the existing ERW pipe manufacturing apparatus has an external bead cutting device, only the second pipe restraining means is provided and the external bead cutting device is provided. If not, the first and second pipe restraining means are arranged in an appropriate position in association with the squeeze roll, while the squeeze roll is simply modified so that the vertical position and the inclination angle can be adjusted. It is possible to produce an ultra-thin ERW pipe having a t / D of 1% or less, which cannot be produced by the method. In addition, when the fusion welding means is provided, it is possible to manufacture a thin-walled welded pipe that cannot be manufactured by the conventional high-frequency preheating combined welding method, and this greatly contributes to the industry.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a principle of preventing edge wave generation in the present invention.

FIG. 2 is a schematic view showing an example of a first pipe restraining means in the present invention.

FIG. 3 is a diagram for explaining the relationship between the positional relationship between each roll and the pipe restraining means and the height of the pass line in the present invention.

FIG. 4 is a diagram illustrating a posture control mode of a squeeze roll according to the present invention.

FIG. 5 is a view for explaining a bending moment generated when a load is applied by moving a squeeze roll up and down on a metal band fixed horizontally at both ends before and after a squeeze roll, and FIG. FIG. 3B shows the bending moment generated when an upward load is applied, FIG. 3C shows the bending moment generated when a downward load is applied, and FIG. 4D shows the bending deformation direction and the generated bending of the metal band. It is a figure which shows the relationship between the positive and negative of a moment.

FIGS. 6A and 6B are diagrams for explaining a bending moment generated when a load is applied to a metal band by the method of the present invention. FIG. 6A shows the positional relationship between fulcrums, and FIG. (C) shows the bending moment when a downward load is applied, and FIG. (D) shows the relationship between the bending deformation direction of the metal band and the sign of the generated bending moment. .

FIG. 7 is a view for explaining a bending moment generated when a load is applied by a squeeze roll when a load is applied to a metal strip by the method of the present invention. FIG. 7 (a) shows the positional relationship of each fulcrum. FIG. 3B shows the bending moment generated when an upward load is applied, FIG. 3C shows the generated bending moment when a downward load is applied, and FIG. 3D shows the bending deformation direction of the metal band and the sign of the generated bending moment. FIG.

FIG. 8 is a diagram for explaining a bending moment generated when a squeeze roll is used as a fixed fulcrum when a load is applied to a metal strip by the method of the present invention. FIG. 8 (a) shows the positional relationship of each fulcrum. FIG. 4B shows the bending moment when the inclination angle θ of the squeeze roll is small, FIG. 4C shows the bending moment when the inclination angle θ of the squeeze roll is large, and FIG. FIG. 4 is a diagram showing a relationship between a bending deformation direction of a bending moment and the sign of a generated bending moment.

FIG. 9 is a schematic diagram showing the overall configuration of an apparatus for performing the method of the present invention.

FIG. 10 is a schematic diagram showing the entire configuration of a conventional welded pipe manufacturing apparatus.

FIG. 11 is a schematic view showing a main part in a method for manufacturing a welded pipe using high-frequency heating means.

FIG. 12 is a diagram illustrating a high-frequency current path when a metal band is heated by the high-frequency heating means.

FIG. 13 is a view for explaining the direction of action of stress generated when the metal band is heated by the high-frequency heating means.

FIGS. 14A and 14B are schematic diagrams showing a deformation mode of the metal band generated when the metal band is heated by the high-frequency heating means. FIG. 14A is a diagram showing a mouth opening deformation, and FIG. .

[Explanation of symbols]

1: roll forming machine, 2: guide roll, 3: breakdown roll,
4: Side cluster roll, 5: Fin pass roll,
5B: Final Finpass Roll, 6:
Squeeze roll, 7: edge part, 8: part other than edge part, 9:
Bottom part, 10: high frequency heating coil,
11: second pipe restraining means, 12: high-frequency heating means,
13: first pipe restraining means, 14: cutting tool, 13 ': support roller, H: metal strip.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-6-39444 (JP, A) JP-A-2-251314 (JP, A) JP-A-61-165225 (JP, A) JP-A 8- 174249 (JP, A) JP-A-7-299516 (JP, A) JP-A-4-167918 (JP, A) JP-A-6-2777752 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B21C 37/00-43/04

Claims (1)

(57) [Claims] 1. A metal strip is formed into an open pipe shape by passing it through a roll forming machine, and both opposing edges are melt-heated by high-frequency heating means and then welded by a squeeze roll, or In a method for welding a welded pipe, which is preheated, then melt-heated using a fusion welding means, and then subjected to abutment welding by a squeeze roll, a pipe restraining means for restraining the welded pipe after the abutment welding downstream of the squeeze roll And at least two of the pipe restraining means are set such that the pass line height of the upstream pipe restraining means is lower than the pass line height of the final fin pass roll of the roll forming machine. It is arranged at a position that satisfies the following formula, and its pass line height and inclination angle are determined by the two pipe restraining means and the final fin pass roll. Method for producing a welded pipe, characterized by adjusting set along the orientation of the strip. L (G + L) / (G + 3L) ≧ J where J: separation distance between the final fin pass roll and the squeeze roll (mm) L: separation distance between the final fin pass roll and the upstream tube restraining means (mm) G: upstream Separation distance between side pipe restraining means and downstream pipe restraining means (mm)